The present invention relates to a laser system and a method of use, and more particularly to a method and an apparatus for a high power laser beam capable of thermally reacting with a target of a rigid material to create cuts and apertures of higher symmetry in the material than heretofore achieved.
Method and apparatus for producing high power laser beams have found many uses and applications in the art, including the use of such a device to scribe or cut a target comprised of a rigid material, such as metals, wood, rubber, plastics or ceramics. By scribing or cutting it is meant that the high power laser beam thermally reacts with the target vaporizing the material to create apertures or holes discretely or continuously in said material. Conventionally, such an apparatus has used a CO.sub.2 laser, operating at 10.6 microns, and having a power output of at least 10 watts. The beam output from such a laser is focussed onto the target material. The target material includes rigid materials such as metals, wood, rubber, plastics or ceramics. Heretofore, it has been felt that the polarization of the beam is unimportant in the application of scribing or cutting of the rigid material. In particular, it was believed that the state of polarization of the beam made no difference in the size or shape of the aperture which resulted from the beam thermally reacting with the material.
U.S. Pat. No. 4,116,542 teaches a method and apparatus for reducing the coherence and for smoothing the power density profile of a collimated high power laser beam, in which the beam is focussed at a point on the surface of a target fabricated of material having a low atomic number. In that patent, it was disclosed that the laser beam incident upon the target material, in one example, was shown to be a circularly polarized beam. However, the use of a circularly polarized beam in that patent served the function of reducing the coherence and for smoothing the power density profile of the laser beam. Moreover, the beam was circularly polarized in order that the reflected beam from the target material would not be reflected back into the amplifier section of the laser, thereby overcoming the problem of potential damage to the laser. It is clear, from a reading of that patent, that it does not teach the particular method and apparatus for a high power laser beam thermally reacting with a target of a rigid material to create symmetrically shaped apertures in the material.
In Applied Optics, Vol. 19, page 2688 (1980), and Vol. 18, page 1875 (1979), a quarter wave reflector using multi-layer dielectric material is disclosed. However, the apparatus and method of thermally reacting a high power laser beam with a rigid material is not taught.
In a paper entitled "Cutting With Polarized Laser Beams" by F. O. Olsen, presented at the German Welding Institute Conference in Essen, in May 1980, and published subsequently in the Digest of that meeting, the author described the influence of the plane of polarization of the beam on the shape of the apertures created thereby.